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HELP! A lot of interference on my wireless rack

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HELP! A lot of interference on my wireless rack

Postby colin.koot » Mon Mar 02, 2020 4:01 pm

I recently build a rack wit 10 wireless headset mics, got it all neatly wired up and solderd an output strip.
But as soon as they're all on, i get alot of signal noices as if they're interfering with each other even tho they're all on different frequencies.

The weird part is, as soon as i unscrew the antennas on the antenna combiner the noice is gone and i can use all of them, but of course a very limited range.
Putting antenna's directly onto the receivers gives me back all the noice.
Ive tryed everything i know at this point,
I hope any of you may help me!
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Re: HELP! A lot of interference on my wireless rack

Postby Sam Spoons » Mon Mar 02, 2020 4:31 pm

Sounds to me as if the frequencies are not correctly coordinated, you can't just use adjacent channels and expect it to work.

What specific frequencies/channels are you using?
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Re: HELP! A lot of interference on my wireless rack

Postby Hugh Robjohns » Mon Mar 02, 2020 4:47 pm

As sam says, it sounds like the receivers aren't operating on compatible channels and are therefore interfering with each other. That cross interference will be stronger with the aerials attached as they will help to cross-couple the radiated signals.

Check the user manuals or the system supplier to confirm which channel sets can be used together.

It would help if you could detail precisely what radio mic receivers you're using, what channels, and how you've wired everything up -- including the Aerial combiner.
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Re: HELP! A lot of interference on my wireless rack

Postby Wonks » Mon Mar 02, 2020 4:48 pm

And could there be other wireless equipment operating in the same band, or maybe even a hearing aid loop?

We'd need to know which country you're in and what equipment (mics and receivers) as well as the frequencies they are set up to.
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Re: HELP! A lot of interference on my wireless rack

Postby colin.koot » Mon Mar 02, 2020 5:52 pm

Already thanks for the reply's!
Im using LDSystems u500 series on the 655 to 679mhz
I used the group and channel functions on the receivers to get them all setup, but this didnt work so i started manually inserting frequenties.
I did read the manual, but al it says is is that yoi can pick a group at channel at your own desire, so that was completely useless.
Im in the Netherlands and checked frequency compatibility when i bought them an they're allowed and should only be in use for wireless mics
Ive got 5 dubbel receivers mounted in a rack with 4 of them going into the LDsystems Win42AD Antenna splitter, and 1 just having its own antennas at the front.
Its all for short range made for a small theater group from around here.
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Re: HELP! A lot of interference on my wireless rack

Postby Hugh Robjohns » Mon Mar 02, 2020 6:19 pm

colin.koot wrote:Im using LDSystems u500 series on the 655 to 679mhz
I used the group and channel functions on the receivers to get them all setup, but this didnt work so i started manually inserting frequenties.
I did read the manual, but al it says is is that yoi can pick a group at channel at your own desire, so that was completely useless. Im in the Netherlands and checked frequency compatibility when i bought them an they're allowed and should only be in use for wireless mics

Sure... there are two issues here. The first is whether the frequencies you are using are legal to use in your geographic area -- and it appears yours are, so that's fine.

The other is whether the frequencies you are using are compatible with each other. The problem is that different radio mic channels cause interference with each other because the harmonics from one overlay the fundamentals of another.

For that reason, it is absolutely critical that you choose a set of frequencies which are compartible with each other... and the more channels you try to run simultaneously, the harder that gets.

The manufacturer, or supplier, or your radio mic administration organisation should be able to advise on which channels are compatible... or you can try and use online calulators, such as this one:

https://ff.audiotechnica.com/cgi-bin/freqcompat.cgi
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Re: HELP! A lot of interference on my wireless rack

Postby Wonks » Mon Mar 02, 2020 6:41 pm

Well, LD say that the 500 systems should support up to 12 transmitters on that frequency. The wording 'up to' is important. The problem with license-free radio bands is that anyone nearby could be using the same bands and so take up some of the capacity.

So if you only use 4 transmitters, do you get the same problem?

If not, if you let the receivers sort themselves out as to a good frequency, how many can you get working before the noise starts?

Or there may simply be a problem with your WIN 42 AD system that is injecting noise into the output signal.

If each individual receiver uses its own aerial, do you still get the same issues? Maybe not practical for stage use, but for testing and fault-finding, can it be done?
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Re: HELP! A lot of interference on my wireless rack

Postby Hugh Robjohns » Mon Mar 02, 2020 6:58 pm

It could also be an issue of having all the receivers crammed in too close to each other. How do they work if you spread them out a bit more?
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Re: HELP! A lot of interference on my wireless rack

Postby Wonks » Mon Mar 02, 2020 7:09 pm

Also, are you powering the receivers fed by the WIN 42 AD from the WIN 42 AD as shown in the LD connection diagram?

https://www.ld-systems.com/en/solutions ... /win-42-ad

If not, you may be creating ground loops which are the cause of the noise. LD are unlikely to provide power outputs on the back of the unit just for the sake of it.

And are you using balanced (XLR to TRS cables) or unbalanced (TS to TS jacks) to connect back to your mixer? Both outputs are line-level outputs, so should not be fed into a mic input (except if using a DI box first).
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Re: HELP! A lot of interference on my wireless rack

Postby colin.koot » Mon Mar 02, 2020 8:12 pm

I could try and space out the receivers, would take me some time tho. It shouldnt be the problem as im using the antenna splitter thats recomended for this kind of use.
Im using the power outs of the antenna splitter and 1 included non-grounded adapter, because i use 5 modules. If i unplug the seperate adapter nothing change to the distortion.

Im using balanced xlr cables, and use an adapter to balanced trs jack into the line input on my desk.
I put my headphones directly into the receiver modules to listen if the problem occurs before it leaves the receivers, and even there i get the same noice and distortion.

I used the frequentie calculator, and it said if you use the standard settings nothing should interfeine.
But it did, so i put some other frequenties in by hand that also shouldnt interfeine and i got a little better results with 5 of them working in stead of 2.
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Re: HELP! A lot of interference on my wireless rack

Postby OTE2020 » Tue Mar 03, 2020 10:57 am

How you put them into a metal rack ? Are you using paddles & aerials ?
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